<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>use_future_t</title>
<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.79.1">
<link rel="home" href="../../boost_asio.html" title="Boost.Asio">
<link rel="up" href="../reference.html" title="Reference">
<link rel="prev" href="use_future.html" title="use_future">
<link rel="next" href="use_future_t/allocator_type.html" title="use_future_t::allocator_type">
<meta name="viewport" content="width=device-width, initial-scale=1">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table cellpadding="2" width="100%"><tr>
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td>
<td align="center"><a href="../../../../index.html">Home</a></td>
<td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td>
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
<td align="center"><a href="../../../../more/index.htm">More</a></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="use_future.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.html"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../boost_asio.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="use_future_t/allocator_type.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_asio.reference.use_future_t"></a><a class="link" href="use_future_t.html" title="use_future_t">use_future_t</a>
</h3></div></div></div>
<p>
        <a class="indexterm" name="boost_asio.indexterm.use_future_t"></a>
      </p>
<p>
        A <a class="link" href="../overview/model/completion_tokens.html" title="Completion Tokens">completion
        token</a> type that causes an asynchronous operation to return a future.
      </p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
    <span class="keyword">typename</span> <span class="identifier">Allocator</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">allocator</span><span class="special">&lt;</span><span class="keyword">void</span><span class="special">&gt;&gt;</span>
<span class="keyword">class</span> <span class="identifier">use_future_t</span>
</pre>
<h5>
<a name="boost_asio.reference.use_future_t.h0"></a>
        <span class="phrase"><a name="boost_asio.reference.use_future_t.types"></a></span><a class="link" href="use_future_t.html#boost_asio.reference.use_future_t.types">Types</a>
      </h5>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  Name
                </p>
              </th>
<th>
                <p>
                  Description
                </p>
              </th>
</tr></thead>
<tbody><tr>
<td>
                <p>
                  <a class="link" href="use_future_t/allocator_type.html" title="use_future_t::allocator_type"><span class="bold"><strong>allocator_type</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  The allocator type. The allocator is used when constructing the
                  std::promise object for a given asynchronous operation.
                </p>
              </td>
</tr></tbody>
</table></div>
<h5>
<a name="boost_asio.reference.use_future_t.h1"></a>
        <span class="phrase"><a name="boost_asio.reference.use_future_t.member_functions"></a></span><a class="link" href="use_future_t.html#boost_asio.reference.use_future_t.member_functions">Member
        Functions</a>
      </h5>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  Name
                </p>
              </th>
<th>
                <p>
                  Description
                </p>
              </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
                  <a class="link" href="use_future_t/get_allocator.html" title="use_future_t::get_allocator"><span class="bold"><strong>get_allocator</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  Obtain allocator.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <a class="link" href="use_future_t/operator_lp__rp_.html" title="use_future_t::operator()"><span class="bold"><strong>operator()</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  Wrap a function object in a packaged task. <br> <span class="silver"> —</span><br>
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <a class="link" href="use_future_t/rebind.html" title="use_future_t::rebind"><span class="bold"><strong>rebind</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  Specify an alternate allocator.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <a class="link" href="use_future_t/use_future_t.html" title="use_future_t::use_future_t"><span class="bold"><strong>use_future_t</strong></span></a> <span class="silver">[constructor]</span>
                </p>
              </td>
<td>
                <p>
                  Construct using default-constructed allocator. <br> <span class="silver"> —</span><br> Construct
                  using specified allocator.
                </p>
              </td>
</tr>
</tbody>
</table></div>
<p>
        The <a class="link" href="use_future_t.html" title="use_future_t"><code class="computeroutput"><span class="identifier">use_future_t</span></code></a>
        class is a completion token type that is used to indicate that an asynchronous
        operation should return a std::future object. A <a class="link" href="use_future_t.html" title="use_future_t"><code class="computeroutput"><span class="identifier">use_future_t</span></code></a> object may be passed
        as a completion token to an asynchronous operation, typically using the special
        value <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">use_future</span></code>. For example:
      </p>
<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">future</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">&gt;</span> <span class="identifier">my_future</span>
 <span class="special">=</span> <span class="identifier">my_socket</span><span class="special">.</span><span class="identifier">async_read_some</span><span class="special">(</span><span class="identifier">my_buffer</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">use_future</span><span class="special">);</span>
</pre>
<p>
        The initiating function (async_read_some in the above example) returns a
        future that will receive the result of the operation. If the operation completes
        with an error_code indicating failure, it is converted into a system_error
        and passed back to the caller via the future.
      </p>
<h5>
<a name="boost_asio.reference.use_future_t.h2"></a>
        <span class="phrase"><a name="boost_asio.reference.use_future_t.requirements"></a></span><a class="link" href="use_future_t.html#boost_asio.reference.use_future_t.requirements">Requirements</a>
      </h5>
<p>
        <span class="emphasis"><em>Header: </em></span><code class="literal">boost/asio/use_future.hpp</code>
      </p>
<p>
        <span class="emphasis"><em>Convenience header: </em></span><code class="literal">boost/asio.hpp</code>
      </p>
</div>
<div class="copyright-footer">Copyright © 2003-2025 Christopher M.
      Kohlhoff<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
</div>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="use_future.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.html"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../boost_asio.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="use_future_t/allocator_type.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
</div>
</body>
</html>
